SOILS

The weathering of the Earth’s surface produces soil.

Adapted from a Soils PowerPoint from Oakland Junior High School in Columbia, Missouri:http://www.columbia.k12.mo.us/ojhs/SOILS.PPT

Formation of soils

A layer of rock and mineral fragments produced by weathering covers the surface of earth. As animals and plants begin to live among these fragments they add waste products and decaying matter to the fragments. This is how the organic part of the soil is formed. Soil is constantly evolving from rock.

SOIL IS MADE OF 2 TYPES OF MATERIAL:

MINERAL MATTERORGANIC MATTER

MINERAL MATTER

The original soil surface Supplies nutrients to green

plants The majority of soils are

composed of three types of minerals

1) Sands – largest particles

2) Silts – smaller particles

3) Clays – smallest particles

The element Carbon

SAND

Sand usually consists of quartz and mica.

It’s a relatively large particle, ranging in size from 0.04 to 0.2 cm in diameter.

Sand is an important part of most soils and is extremely abundant along the courses of rivers, on the shores of lakes and the sea, and in deserts

SILT

Silt is a fine-grained or muddy material made up of tiny particles of rock that settle at the bottom of rivers and other bodies of water.

Silt is made up of particles ranging from 0.004 to 0.0625 millimeter (1/6,500 to 1/400 inch) in diameter.

Most lands with silt deposits are fertile.

CLAY

Clay is a substance present in most kinds of soil.

Geologists define CLAY as extremely small particles of soil that measure less than 4 microns, or 0.000157 inch, in diameter.

ORGANIC MATTER

Consists of dead plant and animal material in various stages of decay.

Decaying organic material releases nutrients into the soil.

Microorganisms like bacteria and fungi help to break down dead matter.

WHICH SOIL WILL BE MORE FERTILE?

OR

The rainforest The desert

THE RAINFOREST

Air Spaces are important in a healthy soil because:

They allow for the circulation of water and air.

A healthy soil has about 50% water and 50% air spaces.

SOIL FORMATION

5 FACTORS AFFECT SOIL FORMATION

1. CLIMATE

2. PLANTS AND ANIMALS

3. PARENT MATERIAL

4. TOPOGRAPHY

5. TIME

CLIMATE

Climate is:

+Temperature Rainfall

TEMPERATURE

Warmer climates cause more rapid decay of organic material. They have better soils.

Cooler climates have less decay of organic material. They have poorer soils.

PRECIPITATION

Some water is good, but too much water is bad for soils.

Leaching – When the soil has too much water and it washes away the nutrients.

PLANTS AND ANIMALS

1. Affect soil formation by providing nutrients from decaying bodies

2. Plants help to retain water so soil doesn’t wash away.

3. Earthworms and other animals help to mix up the soil so it has air pockets.

Mole

Earthworm

PARENT MATERIAL

1. The original “rock” before the soil was formed.

2. The type of minerals present determine the type of soil and the types of plants that will grow in that soil

TOPOGRAPHY

Hilly lands are less fertile because water runs downhill and carries nutrients away

Flat lands are more fertile because water doesn’t wash away as much

Which land below will have better soils?

or

The flat land

TIME

The more time a soil has to develop, the healthier it will be.

4 STEPS TO SOIL FORMATION

1) Bedrock disintegrates

2) Parent material forms

3) Organic matter begins to collect

4) Thick vegetation grows and gives back to the soil.

THE END

THE ENDIs this soil healthy? How do you know?

Adapted from a Soils PowerPoint from Oakland Junior High School in Columbia, Missouri:http://www.columbia.k12.mo.us/ojhs/SOILS.PPT